Various systems and methods are employed to provide inter-chip communication or inter-layer interconnection between multiple layers of, for example, IC circuit chips, in IC packaging. U.S. Pat. No. 4,924,353 to Patraw, incorporated herein in its entirety by reference, reviews, in detail, vast improvement made in the performance of electronic component throughout the electronics industry focusing ultimately on fabrication and further miniaturization of semi-conductor materials and devices and the concomitant packaging problem which such miniaturization brings. Difficulties arise from a number of sources including the fragile nature of the very light gauge wire often used for interconnection, as well as deformation issues which arise from introducing heat and/or stress, e.g., compressive stresses, during conventional fabrication processes. Such difficulties are only exacerbated when individual IC chips or wafers are stacked vertically and interconnection is required between the vertically stacked layers.
Patraw discloses a number of these systems and methods for overcoming the issues associated with inter-layer interconnection and further discusses the drawbacks associated with each. For example, inherent or induced non-planarity of individual chips or wafers may result in ineffective mating between such layers. Based on a non-planarity which may be characteristic of the substrates upon which integrated circuits are formed, it is recognized that elevated contacts with advantageously a characteristic “springiness” may facilitate communication between vertically stacked layers of integrated circuits. Such elevated contacts tend to overcome interconnection shortfalls which arise from characteristic or induced non-planarity in individual chips or wafers as well as environmental concerns, such as, for example, vibration induced in the vertically stacked integrated circuit when operated in its intended environment.
As a solution, Patraw discloses a body of conductive material formed as a pedestal having an upper portion and at least three legs which extend from the upper portion, the legs terminating in flare contact pads which are capable of securely mating to a substantially flat conductive pad in order to form a reliable electrical coupling. Specifically, Patraw explains that the pedestal is formed from a metal which is flexible and will provide an oppositely directed spring tension when the entire pedestal is subjected to a loading force that presses it against an interface pad.